Vol. 5 •Issue 15 • Page 17
The Learning Scope
Fluid & Electrolyte imbalances
Multiple age-related changes affect fluid balance in the older adult
This offering expires July 7, 2005
The goal of this CE offering is to provide nurses with current information about fluid and electrolyte disturbances in older adults that they can apply to their practice. After reading the article, you will be able to:
1. Describe the normal changes of aging that affect fluid and electrolyte balance in the older adult.
2. Discuss laboratory values that differ in the older adult.
3. Discuss common fluid and electrolyte problems experienced by the older adult.
4. Identify prevention strategies for fluid and electrolyte problems in the older adult.
Editor’s note: ADVANCE offers nurses the opportunity to earn continuing education credit by mail or through the convenience of the Internet, which offers immediate test results and proof of credit. To access this test or choose from others, go to www.advanceweb.com and click on the Learning Scope icon. Or mail or fax the answer sheet that follows this article to Merion Publications and receive notification of your test score by mail.
Dehydration is the most common fluid and electrolyte disturbance in older adults. If not detected and treated in a timely fashion, mortality rates may exceed 50 percent. It has been estimated that hospitalization costs for older adults for dehydration in 2000 exceeded $3.76 billion.1 Dehydration along with other fluid and electrolyte disturbances must be considered in the nursing care of the older adult.
Multiple age-related changes affect fluid balance in the older adult. Overall, there is a decreased ability to respond as readily to fluid deficits and excesses. There is approximately an 8 percent decrease in total body water by age 75. While the amount of extracellular fluid remains the same, there is a decrease in intracellular fluid. This results from an age-related increase in adipose tissue that holds less water compared to lean muscle mass. Age-related changes in renal function, such as decreased renal blood flow, decreased glomerular filtration rate and impaired renal diluting capacity, result in less effective concentration of urine, a decreased ability to conserve sodium and potassium and to adjust to acid-base imbalances.2
Medication Administration
The decreased percentage of total body water compared to an increased percentage of body fat has important implications for medication administration in this population. A decreased percentage of body water will increase the concentration of the medication. Likewise, medications that are fat soluble may be more widely distributed, less concentrated and released more gradually into the blood stream. The distribution of medications in the body also is affected by plasma protein. Most medications bind to protein for distribution throughout the body. Older adults have a decrease in plasma protein, particularly albumin, as a result of decreased protein intake in the diet and decreased production by the liver. This can lead to an increased percentage of “free” medication not bound to protein, increased drug activity and toxicity,3 which may predispose the older adult to fluid and electrolyte problems.
In addition, the older adult has a decreased perception of thirst. Many normal older adults are not thirsty even after 12-24 hours without water.2 Usually the older adult is able to maintain fluid balance under normal conditions. Age-related changes become more apparent when disease, medications or environmental stress are introduced.3
In general, there are no significant changes in red blood cells, hemoglobin or hematocrit values as one ages. It is important to recognize, however, that anemia is not normal in the older adult and should be evaluated. There is a decrease in total body potassium with age. Also, the aging kidney is sodium wasting. This can lead to the older adult becoming salt depleted during times of sodium deprivation. Other serum electrolytes and thyroxine (T4) also are relatively unchanged with age.2 However, since the serum creatinine is decreased with age due to a decrease in muscle mass, creatinine clearance determinations provide more accurate reflections of renal function. Changes in the integumentary, cardiovascular and respiratory systems result in the older individual being less able to respond quickly to cooling body temperature, fluid and acid base imbalance, blood loss and shock.3
There is a lack of information about age-related standards with regard to the normal ranges of laboratory values in the older adult. An abnormal value may signify a normal age-related change or a health problem. Attributing these changes to normal aging alone may lead to misdiagnosis and inappropriate treatment.4 All laboratory values should be carefully considered when evaluating the fluid and electrolyte status of the older adult.
Common Disturbances
When older persons experience increased fluid loss or decreased fluid intake, they are at risk for dehydration, the most common fluid and electrolyte disturbance in older adults. Infections, gastrointestinal losses and fever increase this risk, along with the aging changes of decreased thirst perception, decreased concentrating ability of the kidneys, and decreased renin activity and aldosterone secretion.
After loss of as little as 2 percent of body weight, older adults may exhibit nonspecific symptoms of confusion, malaise or disorientation.5,6 Assessment findings may include decreased skin turgor, dry tongue, dry mucous membranes, recent weight loss, sunken eyes, orthostatic hypotension, tachycardia, speech difficulty and increased thirst.7 Serious electrolyte imbalances such as hyponatremia, hypernatremia, hypokalemia and hyperkalemia may result.
Hyponatremia (serum concentration of 135 mEq/L) occurs as a result of an excess of extracellular water relative to sodium. Precipitating factors in older individuals include impaired capacity of the kidney to excrete free water and nonosmotic vasopression release, which are normal age-related changes. Signs and symptoms range from mild complaints of malaise, fatigue, confusion, headache, nausea and decreased functional status to more serious presentations of seizures, coma or death. The severity of the symptoms reflects the movement of water into brain tissue and correlates with the rapidity and extent of the fall of serum sodium levels.5,6
Causes of hyponatremia may be classified by various states. Hypovolemic hyponatremia develops as sodium and free water are lost through renal or nonrenal routes and replaced by inappropriate hypotonic fluids, such as tap water, half-normal saline or dextrose in water. Nonrenal routes include gastrointestinal losses, excessive sweating or third spacing of fluids in conditions such as peritonitis, pancreatitis or burns (see Table).
Euvolemic hyponatremia occurs when sodium stores are normal and there is a total excess of free water, as seen in clients who take in excess fluid (see table). Hypervolemic hyponatremia occurs when sodium stores increase in appropriately. This may result from renal causes, such as acute or chronic renal failure, when dysfunctional kidneys are unable to excrete the ingested sodium load. States of decreased effective intravascular volume may also cause this condition (see table).6
Certain disease states and medications predispose the older adult to developing the syndrome of inappropriate antidiuretic hormone secretion (SIADH). Disorders such as thrombosis, hemorrhage, trauma, malignancies (especially small cell cancer of the lung), inflammatory lung diseases and vasculitis enhance the secretion of ADH by the hypothalamic-neurohypophyseal system leading to SIADH as the primary cause of hyponatremia. Medications, including antidepressants, antipsychotics, ACE inhibitors, diuretics and antineoplastic agents, may also precipitate SIADH by increasing ADH release or by enhancing ADH action on the kidney.6
Whenever low serum sodium levels are asso.ciated with normal or increased serum osmolarity, an underlying cause should be sought such as uncontrolled diabetes mellitus, hypertriglyceridemia or multiple myeloma. In these conditions, total body water and total body sodium are unchanged. Treatment of the un.derlying condition, such as correcting hyperglycemia, will restore the serum sodium to normal levels.5
Hypernatremia (serum sodium levels > 160 mEq/L) occurs when there is a deficit of water in relation to sodium in the body. Regardless of the cause, the primary defect is impaired water intake. Dehydration is the most common cause of hypernatremia in older individuals resulting from the inability to obtain adequate water because of debilitation. As intracellular water shifts to the hypertonic extracellular compartment, the brain experiences cellular dehydration.
Clients with hypernatremia exhibit lethargy, altered mental status, irritability, hyper-reflexia and spasticity. If hypernatremia develops quickly, rapid brain shrinkage may result in intracranial hemorrhage. In chronic hypernatremia, symptoms are milder since the brain has time to adapt.
Treatment for hypernatremia focuses on correction of the underlying cause. If the client is hypovolemic, sodium must be replaced slowly and cautiously in order to avoid cerebral edema.8
Hypokalemia occurs when the serum concentration of potassium is less than 3.6 mEq/L. The most common cause is potassium depletion due to inadequate intake or abnormal losses of potassium (e.g., vomiting, diarrhea, laxative abuse or diuretics).
Herbal supplements that have a diuretic or laxative effect can further compound the problem. These include:
• aloe;
• caraway;
• castor oil;
• dandelion;
• elder flower;
• flax seed;
• figwort;
• glycerol;
• licorice;
• peppermint oil;
• psyllium;
• wheat bran; and
• yarrow9,10,11
Because most clients with mild hypokalemia (serum [K+] 3.0-3.5 mEq/L) are asymptomatic or complain of mild muscle weakness, myalgia and slight fatigue, the condition is usually identified by the presence of low serum [K+] on laboratory testing. Clients with ischemic or scarred cardiac muscle have increased incidence of life-threatening cardiac arrhythmias. Severe potassium deficits may result in rhabdomyolysis, an acute and sometimes fatal destruction of skeletal muscles, and myoglobinuria and if [K+] < 2.0 mEq/L ascending paralysis with eventual respiratory arrest will develop.8,12
Hyperkalemia ([K+] > 5.0 mEq/L) occurs when clients have impaired renal excretion of potassium (80 percent of cases) or when there is impairment of potassium entry into the cells.
While not as common as hypokalemia, im.paired control of potassium concentration makes older adults susceptible to developing hyperkalemia.
Signs and symptoms of hyperkalemia include asymptomatic alterations of normal cardiac conduction patterns. ECG changes include tenting of T waves and widening of QRS complexes (see Figure). Atrioventricular conduction blockage with slow idioventricular rhythms develops, progressing to ventricular fibrillation and standstill. Arrhythmias often occur if potassium increases rapidly.
The most common cause of hyperkalemia is use of potassium supplements or drugs that in.terfere with potassium excretion (e.g., spironolactone) in combination with renal insufficiency. Additionally, conditions (e.g., uncontrolled diabetes, tissue breakdown or metabolic acidosis) or drugs (e.g., digoxin, beta-adrenergic blockers) that impair entry into the cell predispose older adults to hyperkalemia.8,12
Promoting Fluid and Electrolyte Balance
Primary and secondary prevention efforts should be used in all settings where older adults reside to assist clients to maintain fluid and electrolyte balance. The significance of these in.terventions will intensify as the population of older individuals increases, predicted to grow from 12.4 percent currently to 20 percent of the U.S. population by 2030.14
Specific interventions, which will assist older adults to maintain normal fluid and electrolyte balance, are:
1. It is important to assess drug therapy at each healthcare visit including over-the-counter, herbal and prescription medications. Ongoing communication among older adults and their healthcare providers is important for selection and administration of medications that will not cause fluid and electrolyte imbalances. Older adults and their caregivers should be asked if they have noticed any changes in their health status since the last visit or initiation of a new drug regimen.
2. Periodic laboratory screening and healthcare follow-up to assess for signs and symptoms of fluid and electrolyte imbalances and to monitor effects of specific drug therapies and chronic and acute illnesses.
3. Daily minimum fluid intake of 1,500-2,000 mL, spread throughout the day with adequate hydration at meals and pill administration times. Older adults should be encouraged to drink fluids, have access to fluids of their choice and assistance if they cannot drink independently. Nurses should assess factors that may cause older adults to restrict fluid intake such as desire to avoid nocturia or urinary frequency, fear of incontinence, lack of motivation and altered mental status.3 Long-term and acute-care facilities need to provide adequate staff and supervision of ancillary staff to carry out these standards.6,15
4. Older adults require a daily intake of 1,500-2,000 mL of water and a minimum intake of 500 mg/day of sodium.15 Older adults with conditions such as congestive heart failure may need to restrict sodium intake. Older adults generally need supplementation to meet daily calcium requirements because their intake of calcium decreases with age.
Older individuals are at highest risk for the development of osteoporosis. Older individuals should consume 1,200 mg of calcium a day, engage in weight-bearing exercise, and avoid smoking and excessive consumption of alcohol and caffeine to decrease their risk for osteoporosis. They are also at risk for vitamin D deficiency since their exposure to sunlight may be limited, especially during winter months. Aging decreases the ability to synthesize vitamin D, so that the daily intake requirement increases to 15 mcg for older adults. While multivitamins are generally safe adjuncts to the diets of older adults, older adults should take other nutritional supplements only when there are specific indications in order to avoid adverse effects or untoward drug interactions.6,15
5. Cautious use of salt substitutes by older adults who have diabetes mellitus or hypertension along with renal insufficiency or mineralocorticoid deficiency. These products contain potassium, which may predispose older adults for hyperkalemia especially if the older person is also receiving medications that interfere with potassium excretion. Older adults with chronic renal insufficiency or mineralocorticoid deficiency may need to restrict dietary potassium intake to 3 g/day to avoid hyperkalemia.12
Summary
Early recognition of and intervention for fluid and electrolyte disturbances may help prevent functional disability and mortality in older adults.2,4 Prevention of imbalances requires proactive education of the older adult and caregiver to foster adequate fluid and nutritional intake and adherence to periodic laboratory and clinical screening for early detection and correction of disorders.
References
1. Hall, M.J., & Owings, M.P. (2002). 2000 national hospital discharge survey. Advance data from vital and health statistics; no. 329. Hyattsville, MD: National Center for Health Statistics.
2. Taffett, G. (1999). Age-related physiologic changes. In E. Cobb, E. Duthie & J. Murphy (Eds.), Geriatric Review Syllabus, 10-23. Dubuque, IA: Kendall/Hunt Publishing Co.
3. Edlund, B., & Haight, B. (1992). Assessment of the older adult. In J. Bellach & B. Edlund (Eds), Nursing assessment and diagnosis (2nd ed., 776-808). Boston: Jones and Bartlett Publishers.
4. Schretzman, D., & Strumpf, N.E. (2002). Principles guiding care of the older adult. In V.T. Cotter & N.E. Strumpf, (Eds.), Advanced practice in nursing with older adults (pp. 5-25). New York: McGraw-Hill.
5. Davis, K.M., & Minaker, K.L. (1999). Disorders of fluid balance: Dehydration & hyponatremia. In W.R. Hazzard, et al. (Eds.), Principles of geriatric medicine & gerontology, (4th ed., pp.1429-1436). New York: McGraw-Hill.
6. Dudek, S.G. (2001). Nutrition essentials for nursing practice (4th ed.). Philadelphia: Lippincott.
7. Morley, J.E. (2000). Management of nutritional problems in subacute care. Clinics in Geriatric Medicine, 16(4), 817-832.
8. Riggs, J.E. (2002). Neurologic manifestations of systemic disease. Neurologic Clinics, 20(1), 227-239.
9. Rotblatt, M., & Ziment, I. (2002). Evidence-based herbal medicine. Philadelphia: Hanley & Belfus.
10. Fugh-Berman, A. (2000). Herb-drug interactions. Lancet, 335(9198), 134-138.
11. Miller, L.G. (1998). Herbal medicinals: Selected clinical considerations focusing on known or potential drug-herb interactions. Archives of Internal Medicine, 158(20), 2200-2211.
12. Gennari, F.G. (2002). Disorders of potassium homeostasis: Hypokalemia and hyperkalemia. Critical Care Clinics, 18(2), 278-288.
13. Yanowitz, F.G. (1997). Allen E. Lindsay ECG learning center in cyberspace. Retrieved May 3, 2003 from the World Wide Web: http://medlib.med.utah.edu/kw/ecg/index.html
14. U.S. Administration on Aging. (2001). A profile of older Americans: 2002. Retrieved May 3, 2003 from the World Wide Web: http://www.aoa.dhhs.gov/aoa/stats/pro.file/1.html
15. Russell, R.M., Rasmussen, H., & Lichtenstein, A.H. (1999). Modified food guide pyramid for people over seventy years of age. Journal of Nutrition, 129(3), 751-753.
Barbara J. Edlund is associate professor and gerontology track coordinator, and Margaret Spain is assistant professor in the family nurse practitioner program, both at the Medical University of South Carolina, Charleston.
Table: Causes of Hyponatremia6
Hypovolemic States
•Renal insufficiency, acute or chronic in which client is unable to excrete adequate amounts of free water
•Salt wasting nephropathy
•Effects of drugs, such as thiazide diuretics, amiodarone, opiates, oxytocin, vincristine, SSRIs, trazodone, sulfonylureas
•Prolonged exercise in hot weather, especially in clients who drink hyposmolar fluids during exercise
•Excess fluid losses that have been replaced with hypotonic fluids
Euvolemic States
•Excessive fluid intake (10-15 L/day) seen in elderly with psychiatric illness with psychogenic increased thirst
•Administration of hypotonic IV or irrigation fluids in the immediate postoperative period
Hypervolemic States
•Hepatic cirrhosis, congestive heart failure, or nephrotic syndrome, in which clients have insidious increases in total body sodium and free water stores
•Hypothyroidism
•Cortisol deficiency
•Syndrome of inappropriate ADH secretion
•Consumption of large quantities of beer or use of the drug ecstasy Back to story
